Oxide-boride ceramics and their application as cell components in electrolytic aluminum production cells have been disclosed in as yet unpublished U.S. patent applications Ser. No. 454,671 and Ser. No. 454,672 now U.S. Pat. No. 4,540,475. In one example from the application Ser. No. 454,671, a particulate reaction mixture in appropriate stoichiometric amounts for producing titanium diboride and alumina was prepared from titanium dioxide, boron oxide and aluminum. The mixture was hot pressed to form the reaction-sintered alumina-titanium diboride composite. Such reaction-sintered composites are taught to be wettable and resistant to molten aluminum and are therefore suitable for insertion into an aluminum production cell for use as a component which may contact the molten aluminum but preferably remains out of contact with molten cryolite.
It has also been proposed to produce ceramic, which contain metal, by starting with porous ceramic bodies. Such bodies may then be infiltrated with molten metal. Thus in the as yet unpublished U.S. patent application Ser. No. 454,718, it has been suggested to prepare a porous matrix of reaction sintered alumina and titanium diboride. This matrix can then be infiltrated by a molten metal such as molten aluminum to prepare the ceramic with infiltrated metal phase.
More recently in the as yet unpublished U.S. patent application Ser. No. 580,532 it has also been disclosed to prepare ceramic-metal composites (cermets) which may be based upon boride-oxide ceramic. Thus for example in an alumina-titanium diboride composite, excess aluminum over stoichiometric can be present in the reaction mixture and thereby provide residual aluminum metal after sintering. The sintering reaction is carried out with the bulk reaction mixture in contact with molten metal, e.g., molten aluminum, which can thereby supply further aluminum to the ceramic body. The sum of all of this aluminum, plus the reaction sintering, achieves the cermet preparation. Also, some preformed ceramic can be present in the reaction mixture prior to sintering, and thereby later reside in the cermet.
It would however be most desirable to use not only inexpensive reactants but also to achieve economy of operation to produce a cermet by straightforward operation.